Electrical switches serve to switch electric currents. IEC-certified and UL-certified variants are typically available. Known types of UL-certified switches include those which are installed directly into a so-called panel board. Special UL-certified switches of this kind are also called low-tab switches.
An electrical low-tab switch comprises a pole cassette package, a housing upper part, an accessories cover and a thermomagnetic trip unit (TMTU). A housing lower part for an electrical low-tab switch is not required, or a housing lower part is replaced by the so-called top barrier which is installed in the panel board. A plurality of switches can be installed into the top barrier next to one another, wherein the top barrier ensures insulation between the phases within a switch and between various switches.
Since a housing lower part cannot be installed, it is necessary for both the panel board and the housing upper part to also take on the function of the housing lower part.
A housing upper part typically has to ensure, amongst other things, that the air and creepage paths correspond to the standards, and the rotors of the pole cassette are covered. Therefore, the housing upper part has two side walls which project downward to a great extent. In the event of a short circuit with the creation of an arc with a plasma, these side walls would be bent or even destroyed if they were still additionally fixed.